8 Transactions of the 



which appeared to be the sole organ of locomotion. When under 

 the cover-glass in the moist chamber they persistently formed a 

 ring, about a hundredth of an inch from the edge of the cover all 

 round, leaving the middle of the cover to mere stragglers and other 

 forms.* The object appeared to us to be to get as near as possible 

 to the source of oxygen. Fission was as frequent and striking 

 amongst them as in the other cases we have pointed out ; but its 

 first indication was a sluggishness of motion, and the appearance of 

 a whitish semi-opaque spot in the sarcode under the hook, as seen in 

 Figs. 2 and 3, ibid., and at the same moment it would become squarish 

 and amoeboid all over, as seen in these figures. At the same time 

 the spot a, Fig. 2, repeatedly opens from a median hne nearly to its 

 margin (revealing no internal structure), and suddenly snaps to- 

 gether again like the rapid closing of the eyelid. This is a pheno- 

 menon the nature of which has entirely defied our most careful and 

 untiring inquiry, and it is one that has presented itself in several 

 forms.f In his paper on " Proioeoccus pluvialis" ('Ray Soc.,' 

 1853), Cohn says (p. 534) that the protoplasm "possesses the 

 faculty of forming vacuoles at all times, and even externally to the 

 cell ; a property, it is true, which has for the most part been hitherto 

 overlooked or misinterpreted." To which the editor, G. Busk, adds, 

 " sometimes, as in the zoospores of volvox, these vacuoles exhibit 

 rhythmical contraction." Whether this is a phenomenon similar 

 to the one we describe above, our examination of volvox has not 

 enabled us to decide, but it is a feature deserving careful and com- 

 petent research. 



If now a power of about 4000 diameter be used, and the light 

 carefully manipulated, another oval spot h, Fig. 2, will be seen, but 

 ivithout either the opening or shutting seen in a. Constriction 

 now presents itself as at a, h, Fig. 3, and this gradually increases, 

 as seen in Fig. 4 of the same Plate, where the monad has turned 

 round in the process of fission, but the letters a and h stand for the 

 same parts as in Fig. 2. Before the division had proceeded further, 

 we were in our earlier examinations surprised by the sudden appear- 

 ance of the hooked and the trailing flagella on the side h (originally 

 of course without it) of the form, as drawn at Fig. 4. How this 

 came was at the time inscrutable to us. The progress of the 

 division was now rapid, and by focussing down or up and using the 

 light with care, we were enabled to see the stretched filament 

 between them as drawn in Fig. 5 ; but when this snapped it was 

 wholly lost to view, and we could see no trace of it again. In- 

 deed, it was not quite clear that it did not snap off at a and h, 

 and become wholly detached. To this question we paid close and 

 continuous attention, and after many days of observation we were 



* This is not peculiar to this form, but is more manifest than in most others, 

 t ' Microscopical Journal,' p. 203, Nov. 1, 1873. 



